Found this flow chart and explanation on Zero Hedge, petrocurrency mercantilism is when a national bank and an energy producer collude to generate artificial demand for a currency at the expense of the purchasing power of other currencies.

Pretty fascinating when you think examine all the tools available for a petrostate.

From http://www.zerohedge.com/news/2015-03-03/petrodollar-mercantilism-explained-one-simple-chart